221421661 has 4 divisors (see below), whose sum is σ = 221451424. Its totient is φ = 221391900.

The previous prime is 221421659. The next prime is 221421671. The reversal of 221421661 is 166124122.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 221421661 - 2¹ = 221421659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221421671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7216 + ... + 22246.

It is an arithmetic number, because the mean of its divisors is an integer number (55362856).

Almost surely, 2^221421661 is an apocalyptic number.

It is an amenable number.

221421661 is a deficient number, since it is larger than the sum of its proper divisors (29763).

221421661 is a wasteful number, since it uses less digits than its factorization.

221421661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29762.

The product of its digits is 1152, while the sum is 25.

The square root of 221421661 is about 14880.2439832148. The cubic root of 221421661 is about 604.9786309416.

Adding to 221421661 its reverse (166124122), we get a palindrome (387545783).

The spelling of 221421661 in words is "two hundred twenty-one million, four hundred twenty-one thousand, six hundred sixty-one".